1. Field of the Invention
The present invention relates to a substrate processing apparatus, a method of manufacturing a semiconductor device, and a method of confirming an operation of a liquid flowrate control device, which are adapted to manufacture a semiconductor device by performing processes such as a thin film forming process, an oxidation process, an impurity diffusion process, an annealing process, and an etching process on a substrate such as a silicon wafer.
2. Description of the Related Art
In a substrate processing process, a liquid mass flow controller and a vaporizer are used to perform a film forming process in which a liquid source is supplied while vaporizing to form a thin film on a substrate. For example, when a zirconium oxide film is formed, tetrakis ethylmethyl amino zirconium (TEMAZ) is used as a Zr source and ozone (O3) is used as an oxygen source. However, TEMAZ is a liquid at ordinary temperatures and pressures (room temperature), and is supplied into the vaporizer by the control of the liquid mass flow controller. Then, the TEMAZ is vaporized in a vaporizer chamber inside the vaporizer to supply the vaporized TEMAZ gas together with an inert gas of a carrier into a reaction chamber as gas.
Among substrate processing apparatuses, in a batch type apparatus in which fifty sheets to hundred fifty sheets of substrate are processed at one time, it is necessary to supply a relatively large amount of TEMAZ. As a method for supplying a large amount of gas, a source tank itself may be heated to increase a vapor pressure. However, since the TEMAZ is a material that can be easily thermal-decomposed, it is difficult to heat the source tank for a long time. In addition, since the TEMAZ is a liquid having a low vapor pressure, it is difficult to obtain a sufficient flowrate using only its own vapor pressure without heating.
As a result, the TEMAZ is used through a method using the vaporizer in which the TEMAZ is in a liquid state at room temperature within the source tank and is vaporized by heat only in the vaporizer.
In such a TEMAZ supply system, a solvent supply system is provided also. When a line member through which the liquid TEMAZ passes is replaced, since the TEMAZ has a low vapor pressure, it is actually impossible to remove the source using only vacuum exhaust and N2 purge. Thus, a solvent having a vapor pressure greater than that of the TEMAZ even though it is in a liquid state at room temperature, for example, normal hexane (n-Hexane) flows to downwash the TEMAZ, thereby performing a line cleaning process. The n-Hexane does not react with the TEMAZ and melts the TEMAZ. In addition, the n-Hexane is easily evaporated because it does not react with components of the atmosphere.
FIG. 6 is a graph illustrating a saturated vapor pressure curve of TEMAZ and n-Hexane. The TEMAZ has 0.004 Torr at a temperature of 30° C., and the n-Hexane has about 180 Torr at a temperature of 30° C. As a result, it may be seen that the TEMAZ and the n-Hexane have a four-digit or more vapor pressure difference therebetween.
In a related art substrate processing apparatus, when a liquid mass flow controller is used firstly (including also when the liquid mass flow controller is used firstly after being replaced), it is necessary to confirm an operation state of the liquid mass flow controller in a state where the liquid mass flow controller is installed in a batch type apparatus. However, for confirming the operation state of the liquid mass flow controller, when the TEMAZ as a source flows actually, in case where non-restorable defects exist in the liquid mass flow controller, the liquid mass flow controller should be replaced. In addition, since processes such as a liquid removal process→a purge process→a cleaning process using the solvent→a purge process are required, it takes a long work time.
Also, although the cleaning process is performed with a sufficient time and a deliberate sequence, since there is a chance that a slight amount of liquid remains, it may be possible that the pipe may be contaminated by the reaction between atmosphere and the residual source during replacement works.